Individuals may utilize communication networks for voice communications, research, entertainment, or for conducting critical business transactions. Users of communication networks also frequently request multimedia content via the networks in real-time, often referred to as streaming media. An internet protocol multimedia subsystem (IMS) is a network architectural framework that supports these streaming media sessions and other types of communication services.
IMS is designed to enable delivery of real-time multimedia services in the internet protocol (IP) to communication devices operated by users requesting these services. IMS typically utilizes the session initiation protocol (SIP) to facilitate communication session setup and tear-down. IMS assists in providing access to multimedia and voice applications for both wireless and wireline communication devices, which is commonly referred to as fixed-mobile convergence. Essentially, IMS operates as a horizontal control layer that isolates an access network from the service layer that provides the content or services requested by the users. Therefore, an IMS core network architecture provides access aggregation for several different access networks, and can be utilized to provide communication services from the service layer independent of the underlying access technology employed by a user or network. In order to invoke a communication service for an IMS user, initial filter criteria (IFC) is processed to determine when a particular application server should be contacted to provide the communication service.